Fluidized fixed bed process



Dec. 29, 1953 P. w. CORNELL FLUIDIZED FIXED BED PROCESS Filed Aug. 25,195o IN VEN TOR. PAUL W. CORNBELL ATTORNEY Patented Dec. 29, 1953FLUIDIZED FIXED BED PROCESS Paul W. Cornell, Mount Lebanon, Pa.,assignor to Gulf Oil Corporation, Pittsburgh, Pa., a corporation ofPennsylvania Application August 25, 1950, Serial No. 181,431

3 Claims. (Cl. .2S-1) This invention relates to catalytically promotedchemical reactions and more specifically to catalytic chemical reactionswherein the reaction is carried out under elevated pressure and whereinthe heat of reaction ranges from substantially neutral to exothermic. Myinvention has particular utility in chemical reactions involving theconversion of hydrocarbons.

In connection with the conversion of hydrocarbons it has heretofore beenknown to carry out the conversion by means` of xed `catalyst bed typeprocesses. In this type of process, preheated hydrocarbons areintroduced into a reactor containing a stationary bed of retractorycatalyst in the form of relatively large pellets. The heatedhydrocarbons are intimately contacted with the catalyst within thereactor, following which, converted hydrocarbons are withdrawn from thereactor. At the end of the on-stream cycle the charge stock flow isstopped and regenerating gases are passed through the catalyst bedwithin the reactor. One advantage of this type of process is that thecatayst may be utilized to the entire extent of its activity, e., theon-stream cycle need not be stopped until the activity of the catalysthas been substantially entirely reduced. Another advantage of this typeof process is that the catalyst regeneration may be carried out underoptimum conditions, since the regeneration conditions are not aiiectedby the reaction conditions. Another advantage of the Xed bed type ofprocess is that the reaction may be carried out at very high pressure,if desired. One inherent diiliculty of the fixed bed type of process isthat the expensive reactor is made more expensive by being made suitablefor both the conversion reaction and regeneration. Furthermore, it maybe necessary to comprise the optimum reactor -design in order to suitregeneration requirements, or vice versa. Another difficulty connectedwith this type of process is that coke laydown, a carbonaceousdeposition, usually occurs and often results in partial or completeclogging of the catalyst bed. If the clogging of the catalyst bed isonly partial, hot spots within the bed are developed during regenerationwhich may result in damage to the catalyst due to overheating. If theclogging is substantially complete, it may be impossible to regeneratethe catalyst bed, simply because it is impossible to pass regeneratinggas therethrough. Another dilculty involved in this type of process isthat of supporting the bed of catalyst within the reactor. This element,i. e., the catalyst support, is a continuous sour-ce of difliculty inthe operation of fixed bed processes. In the regeneration of fixedcatalyst beds, it is usually necessary to employ an inert cooling gas,or other cooling medium in order to prevent catalyst destruction orphysical injury to the reactor. The use of such cooling methods areundesirable since they require additional expensive equipment.

It has also been known to catalytically convert hydrocarbons byconventional iiuidized processes. In carrying out this type of process,preheated hydrocarbons are introduced into a reactor wherein a nelycomminuted refractory catalyst is maintained in a nuidized form, i. e.,a turbulent state of suspension. The heated charge stock is intimatelycontacted with the catalyst employed, and converted hydrocarbons arecontinuously withdrawn from the reactor. Also, partially spent catalystis continuously withdrawn from the reactor and conveyed to an adjacentregenerator where the catalyst is regenerated. Likewise, hot regeneratdcatalyst is continually conveyed from the regenerator back to thereactor. It will be seen that throughout the process there is acontinuous ow of charge stock into the reactor and a continuous flow ofhydrocarbons out of the reactor, while uidized catalyst continuouslyvpasses into and out of the reactor. In the operation of this type ofprocess, the catalyst remains within the reactor for a comparativelyshort time and is never substantially completely deactivated. However,it should be noted that it is necessary to continuously withdrawcatalyst prior to its complete deactivation, since cracking reactionsare endothermic. The withdrawn regenerated and reheated catalyst isreturned to the reactor and supplies the necessary additional heat tokeep the reaction going. It should also be pointed out that this is theonly practical way to supply heat to the reactor. Therefore, it will beseen that one inherent diiiiculty in the conventional luidized catalyticcracking process is that the catalyst can never be utilized to the fullextent of its activity. One other inherent difficulty in the processdescribed above is that it cannot be operated economically at pressuressubstantially above atmospheric.l This is true, since it is uneconomicaland very diicult to maintain a continuous rlow of catalyst from thereactor to the regenerator and back again under high pressure. It has inthe past been considered equally impractical to continucusly removecatalyst from a high pressure reactor, regenerate it at low-pressure,and cons tinuously return it to the high pressure reactor. In addition,it will be seen that the conventional n nuidized processes are ofnecessity limited to approximately identical reaction pressures andregenerating pressures, which conditions may not always be mostdesirable for most efficient performance.

One object of this invention is to provide an improved process forcarrying out catalytically promoted chemical reactions having a heat or"reaction ranging from approximately neutral to exothermic. Gne otherobject of this invention is to provide an improved regenerating methodfor fluidized-ixed bed processesv involving a chemical reaction whereincarbonaceous deposition on the catalyst occurs rapidly and/or to a greatextent. Another object is to provide a conversion process whereinregeneration oi the catalyst is less of a problem, sincethc possibilityoi plugging of the catalyst bed through coke laydown is eliminated. Afurther object is to provide an improved pressurized catalyticconversion method whereby the catalyst may be regenerated atsubstantially atmospheric pressure. A still further object is to providea catalyst regeneration method wherein the need for an inert cooling gasduring regeneration is eliminated, since the danger of catalyst damageresulting from overheating during regeneration has been lessened.Another ob ject is to provide a process for carrying out a catalyticconversion under pressure while regeneru ating at a substantiallydifferent pressure. other object is to provide a more economical processi'or converting reactant vapor under pressure by regenerating thecatalyst in a vessel separate from the reactor. Still another obiect ist'o provide an apparatus in which the structure of the conveyor systembetween reactor and regenera tor is not dictated by the .amount of heatto be transferred to the reactor. An additional object isI to provide acontinuous process and suitable apparatus therefor, embodying theobjects listed above. Other objects will appear hereinafter.

These objects. are accomplished by my invention which comprises aprocess for catalytically promoting a chemical reaction having a heat ofreaction ranging from approximately neutral to exothermic and in whichthe catalyst is reactivated by oxidation, said process including thesteps of maintaining powdered refractory catalyst in a state ofturbulent suspension within a reaction chamber, and contacting saidcatalyst with reactant vapor under conditions oi elevated temperatureand pressure. Converted product is continuously withdrawn from thereactor while substantially all of the catalyst is. retained within thereaction chamber. The reaction cycle is terminated when the activity ofthe catalyst has been substantially reduced. The chamber is thendepressured and the catalyst removed to a regenl erating zone. Thecatalyst is regenerated by oxidation at a substantially lower pressureand at elevated temperature. The catalyst is then reused to promote anapproximately neutral to exothermic chemical reaction. My invention alsoincludes suitable apparatus for carrying out this method.

It will be seen that my invention combines the best features of theconventional fluidized type process with the best features of the xedbed type process, without carrying over any of the inherent difficultiesof either.

In the accompanying drawingr is shown a non' diagram of one suitableapparatus for carrying out a specific embodiment of my intention,

In the accompanying description certain preferred modications of myinvention have been set forth. However, it will be understood that theseare by way of illustration only and are not to be considered aslimiting.

In general, my process is applicable to any catalytically promotedchemical reaction whose heat of reaction varies from exotherrnic toappro-. mately neutral, which employs elevated reaction pressure, andwherein the catalyst becomes deactivated and is regenerated byoxidation. Examples of exothermic reactions answering this descriptionare: the hydrogenation of aldehydes, thehydrogenation oi phenol tocyclohexanol, and the hydrogenationoi carbon monoxide to meth ane..Examples of exothermic hydrocarbon conversion reactions carried outunder elevated sure-are non-destructive hydrogenation and additionreactions such as polymerization. lviy inn vention is equally applicableto processes having a heat of reaction which is approximately neutraland which are carried out at elevated pres sure. Examples of this typeof reaction are those in which an exothermic reaction such one of thoselisted above takes place simultaneously with an endothermic reactionsuch as catalytic craching, thereby producing a substantially neutralheat balance. Specific examples ci this type of reaction arehydrocracking or destructive hydrogenation and hydrodesulfurization. Ineach of these reactions endothermic catalytic cracking takes place atthe same time as the exothermio hydrogenation, thus producing what maybe termed an approximately neutral or slightly exothermic reaction. Myinvention is also applicable to certain endothermic catalytic conversionprocesses which may be carried out in such a manner as to produce asubstantially neutral heat balance, e. g. by preheating the reactantvapor to the necessary degree. Examples of endothermic reactions whichmay be operated in an ap proximately neutral heatrbalance region are hydroformlng and catalytic reforming in the presence of hydrogen.

Referring now more particularly to the drawing, charge stock, shown inthe drawing as crude oil, is introduced into the system through line i.The charge stool; passes through pump throng line l, line E, throughheat exchanger 8 and into heater Il). The other reactant, shown in thedrawing as hydrogen, enters the system through line H. The freshhydrogen compressed in hydogen compressor l2 from which it passes intoline Hithrough valve and into line 5, where it is mixed with the chargestock. The hydrogen along with the charge stoolsl passes from linethrough heat exchanger 6 and into heater it. The mixture of hydrogen andcharge stock passes out of heater l@ through line 2B, into line iiithrough valve 22, through line 23 and into reacto- Zit where it iscontacted with hot, iinely divided hydrogenating catalyst maintained ina fluidized state under elevated pressure. The catalyst bed ismaintained in iiuidiaed form by the flow oi charge stock vapors andhydrogen therethrough and is substantially unrenewed during the onstreamperiod.

Regardless oi the nature of the charge stock, some of this material willalways be in vapor form due to the preheating in heater iii and heatexchanger 3. However, in the oase of heavier: charge stocks such astotal crude, a portion of the total charge may be inliduid form wheninitially charged to the reactor'. It is possible that aconsiderableportion of such liquid charge stock is adsorbed in the poresof the catalyst particles without wetting them suiciently to causeagglomeration. Y

In instances where reactor |58 is on-stream, preheated hydrogen andcharge stock pass from line 2li into line |92, through valve its andinto reactor |58. In instances where reactor 2t? is on-stream, preheatedhydrogen and charge stock pass from line 20 through valve 23B and intoreactor 262. A larger or smaller number of reactors may be used asdesired.

While the charge stock is within the reactor, it is intimately contactedunder conditions of heat and pressure with the extremely large surfaceof the catalyst particles. Converted hydrocarbons and a small amount ofcatalyst nes are continuously withdrawn from reactor 2li throughopenings 25 and 2B positioned in cyclone separators 3|! and 32. Theportion of catalyst entering the cyclone separators along with theconverted hydrocarbons is desirably only a small proportion of the totalcatalyst and is chiefly composed of fines produced by attrition. Thebulk of the catalyst remains suspended in the lower part of the reactorthroughout the entire onstream period. The catalyst fines are separatedfrom the converted hydrocarbons within the cy clone separators and arereturned to the reactor through standpipe 25. Converted hydrocarbonspass out of reactor 21| into line 3ft, through valve 36 and into line38. In instances where reactor |58 is on-stream, converted hydrocarbonsand some powdered catalyst are withdrawn through openings |65 and |68;powdered catalyst is separated from the converted hydrocarbons incyclone separators |62 and |54; catalyst is returned to reactor |58through standpipe loll, and converted hydrocarbons substantially free ofcatalyst pass out of the reactor into line llo through valve VEB andinto line 38. In instances where reactor 2&2 is on-stream, continuousstreams of converted hydrocarbons and some powdered catalyst arewithdrawn from the reactor through openings 2||l and 2|2, positioned incyclone separators 206 and 288. Powdered catalyst is separated from thestream of hydrocarbons Within the cyclone separators and is returned tothe reactor through standpipe 20d. Converted hydrocarbons then pass outof reactor 202 into line 2id, through valve 2 I6 and into line 38. Fromline $8 the converted hydrocarbons are partially cooled by passingthrough heat exchanger 8; they then pass through line d and are furthercooled in cooler 42. The cooled converted hydrocarbons then pass intoline i4 and into high pressure separator 65. Hydrogen and hydrocarbongases separate and pass from high pressure separator e into line 5c,through recycle hydrogen compressor l5 into line |8. This mixture ofhydrogen and hydrocarbon gases is pure enough to use as recycle hydrogenbut may be further purified to concentrate the hydrogen by means of anabsorber (not shown). The recycle hydrogen is then recycled into thesystem by passing it through valve 2li@ into line A portion of the watercontained in the product within separator 46 collects in water trap 52and is withdrawn through line 54, through valve 56 and through line 5t.The converted and condensed hydrocarbon product then passes out of highpressure separator 46 into line llt, from which it is introduced into alow pressure ilash drum and other conventional product recoveryequipment (not shown), by means of which the liquid hydrocarbon productis separated into various fractions.

At the termination of the on-stream cycle the flow of oil is out out ofthe reactor and hydrogen flow is continued through the reactor to purgethe chamber of hydrocarbons. In the accompanying schematic drawing thismay be accomplished by stopping the operation of pump 2, whereuponhydrogen continues to pass from line 20 through line 2|, through valve22 and line Z3 into reactor 2d. More generally however, valve 22 isclosed, and valves Lifts and 2de are regulated to divert at least aportion of the recycle hydrogenrich gas from line it into line 250through valve 248 and into line 252. From line 252 the recycle gas flowsthrough heater 25s into line 25.5 and into line IBS. When desired,valves 258 and 26o may also be regulated to divert a p01'- tion of thefresh hydrogen from line is through valve 26u into line 252 by way or"line 2&2. From line |3i! the recycle gas or recycle gas plus freshhydrogen passes into line |32 through valve |36 into line |36 and intoreactor 2li. The hydrogen employed in the purging step, as well as thehydrocarbons removed from the reactor, pass out of the reactor into line38 and follow the saine course described for the converted hydrocarbons.At the end of the hydrogen purge, in instances where hydrogen for thehydrogen purge was introduced through line 2G, valves 22 and 36 areclosed and valve Hl is opened. In instances where hydrogen for thehydrogen purge was introduced through line |39, Valve is has alreadybeen closed, but valves 'M3 and/or 239 must be closed in addition. Valve36 is then closed and. valve Uitl is opened. In either instance, thereactor is depressured into the low pressure separator (not shown)through line |33, valve Ulti,

-line |152, line |44, line |46, valve M8, and line ld. Valve l 48 isclosed and steam is then passed through line |30, through line 32,through valve 34, into line |36, and into reactor 2d. The steam andother gases contained in the chamber pass out of reactor 2li throughline 3ft, line |38, through valve |49 into line m2, into lines les andM2, through valves 2M, and are vented through line 246. In instanceswhere the onmstream and hydrogen purge cycle of reactor |58 areterminated, and where hydrogen for the hydrogen purge has been drawnfrom line 2d, valve |74 is opened and valves itil and llt? are closed.Where hydrogen for the hydrogen purge has been drawn from line |39,valve it@ will have already been closed, but it is also necessary toclose valves 2% and/or 25). Valve llt is then closed, and valve ileopened. In either instance, the reactor is depressured to the lowpressure separator (not shown) through lines il@ and |12, through valveiid, lines H5, illl, and i136, through valve Hi8, and into line i523.Valve |63 is then closed and steam is passed from line |39 through line2do, through valve |98, into line |96 and into reactor ist. The steamand other gases contained in the reactor pass out of the chamber throughline llt, into line H2 through valve Vit, into line Ils, and into linehill. From line |46 these gases pass through line M2, valve 2li!! andinto line 2de, from which they are vented. In instances Where theonstream cycle and hydrogen purge of reactor 2t? are terminated andwhere hydrogen for the hydrogen purge has been drawn from line 2d,valves 23S and 2id are closed and valve 22E) is opened. In the instancewhere hydrogen for the hydrogen purging has been drawn from line |351,Valve 23S will have already been closed, but it is also necessary toclose valves 2433 and/or 269. Valve 2l5 is then closed and valve 22eopened. In either event, the reactor is depressured into the loWpressure separator (not shown) through lines 2 l 4 and 2i 8, throughvalve 22d, lines 222, Mii and H3G, through valve i132 and into line loa.Valve Hi8 is then closed and steam is passed from line itil throughvalve ttt, into line 238 and into reactor 2&2. The steam and other gasesow out of the reactor into line 2id, line 2te, through valve 22d intoline 222 and into line idd. From line lill-'i these gases into line2G32, through Valve Z-i and into line from which they are vented.

At this point catalyst is removedfrorn the reactor and conveyed to theregenerator, This is accomplished in reactor 2:@ hy closing valve i3dand opening valve 52. Steam, lue gas, or air is passed through linei'E-. Catalyst from reactor fili passes from the reactor into line ld,through valve through line and into line IE5. In instances where thecatalyst within reactor is to be regenerated, valve i533 is closed andvalve its is Catalyst then passes from reactor 53 through line throughvalve 88 into line Eto and into main conveyor line 56. In instancesWhere reactor has been on-strearn, valve 2F53' is closed and valve Etzis opened. Catalyst contained in the reactor passes into line 23ethrough valve 23E into line 23s and into main conveyor line 95E.

The spent catalyst and gaseous conveying medium flows from line H55 intoregenerator Where the catalyst is regenerated by combustion oi thecontaminants with air or other oxidizing gas. In the modification shownin drawing, air is introduced into the regenerating system throughopening le, through pump '325, into line 89, through line 82 and valvei3 and into air heater 85. A portion of the air from line is divertedinto line te through valve t to supply air to the burner oi the airheater. Air heated by the heater passes through valve e! into line 3d,through line ed and into regenerator iid, Where it is used to initiatethe burning oir of the contaminants on the catalyst. Once theregeneration is started, i. e., after the burning has commenced, burnerSe is blocked oil by closing valves Ei, di, and d5. Valve il is openedand unheated air is bypassed around the heater through line Thisbypassing is possible, since, once started, the regeneration is eX-othemic, no additional heat is required.

In some instances, as will be hereinafter described, the regeneration ofthe catalyst involves not only burning off the carbon but alsoreconverting the catalyst to the oxide form. A continuous flow of fluegas containing some regenerated catalyst passes through openings H32 andWe into cyclone separators 9S and itc. Preferably, only a portion 0; thecatalyst enters the cyclone separators, with the bull: of the catalystbeing maintained in a duidised state in the lower portion of theregenerator. A substantial portion of the powdered catalyst contained inthe flue gas is separated and returned to the catalyst regeneratorthrough standppe t5. Flue gas a very small portion of regeneratedcatalyst pass out of the regenerator into line d and into trim coolerles. Frorn trim cooler tot? the iiue gas and the very small portion ofregenerated catalyst pass through line il! into Cottrell precipitatorit, where the last portion of catalyst is separated from the .fluegases. ilue gas passes out of the Cottrell precipitator through line H4,through valve I6 and into line H8. Regenerated catalyst which has beenrecovered in the Cottrell precipitator is withdrawn at the bottomthereof through line- I2 l, through valve |23 and line 25. In order toremove the heat of combustion of the contaminants and preventoverheating of the catalyst Within the regenerator, a means oicontinuously cooling the catalyst during regeneration is provided. Aportion of the catalyst within the regenerator passes into collectorH20, through line E22, and into cooler 121i. A portion of the air fromline 88, or line 8S after burner 8B has been blocked oil, is divertedthrough line t28 and into cooler 124 in order to provide means fortransporting thecatalyst from the cooler back through line $26 into theregenerator.

.After the catalyst has been transferred to the regenerator, and afterat least a portion oi the regeneration has been completed, the conveyingsystem is reversed, and catalyst is reconveyed to a reactor. Steam isintroduced through line 92 in order to strip the regenerated catalyst oiue gas. Valves 96, mi and @E are opened. A portion of the steam isdiverted from line through line 94, through valve 9e and into line 52.rIhis steam serves in part to strip the catalyst in line 52 but isemployed principally to areatethe column of catalyst and thus preventpacking. Steam passes from line t3 through valve E5 and into line iiii.This steam is used to convey the regenerated catalyst. The regeneratedcatalyst and its transporting medium, st 1. pass from line E5 intocooler 63 and into line it.

At this point it Will be seen that one of several modifications may bepracticed. For example, regenerated catalyst may be introduced into theconveyor system from cooler i241 and line However, in that event airwould be the conveying medium. Since steam is the preferred transportingmedium, the illustrated vrnodication which employs an additional triincooler G'i is preferred. In addition, I contemplate employing a line 89and valve i5? connecting 'the reactor side of cooler 68 with regenerator5d. By means of this line and valve, regenerated catalyst could berecycled into the regenerator during such periods as no regeneratedcatalyst is being transported to the reactors. The pur pose of thismodification would be to keep a continuous flow of hot catalyst throughtrim cooler $8 and thus eliminate thermal strains which would otherwisebe produced.

In the instance where reactor 'fifi nlled with regenerated catalyst, thecatalyst and its conveying medium, steam, pass from line 10 throughvalve "i2, into line li and into reactor 2li. In instances Where it isdesired to rei'lll reactor 53 with regenerated catalyst, the catalystand transporting medium pass from line 'l0 into line i322, through valve$32, through line 184 and into the reactor. .In stances Where it isdesired to rerlll reactor with regenerated catalyst, the catalysttransporting medium pass from line 'it thi-ou line 22d, through valve225, through line 22d a into the reactor.

is to he reregenerated.

In each case the steam e' ployed in conveying the catalyst to the rea isvented through line 245.

When the desired reactor, for example reactor: 2d, has been refilledwith regenerated Catal; valve 2 is closed; the reactor is blocked oiclosing valves 22, 36, and ifi@ and is then iepressured, for instance bypassing hydrogen or propane through line |30, into line |32, throughvalve |34, through line |36 and into the reactor. In instances where thereactor |58 has been refilled with regenerated catalyst, valve ISE isclosed and the reactor is blocked off by closing valves |14, |13 andIIIIi. rEhe reactor is then repressured by passing hydrogen or propane,for example, through line Itl, into line 2st, through valve |98 intoline |96 and into the reactor. In instances where reactor 232 has beenrelled with regenerated catalyst, valve 225 is closed and the reactor isblocked olf by closing valves 2I6, 220 and 236. The reactor is thenrepressured, for example by passing hydrogen or propane through line|36, through valve 25N) into line 238 and into the reactor. Afterrepressuring, the flow of hydrogen and charge stock is cut into thereactor.

A typical operating cycle for a system as illustrated, which employsthree reactors (or a multiple thereof) and a Li-hour processing period,might be as follows: Oil is cut into reactor 24 and out of reactor 202which has been ori-stream for four hours. At this point, reactor |563has been operating for two hours, and, like reactor 24, is operatingunder conditions of elevated temperatureA and pressure, for example 850F. and 500 p. s. i. g. Hydrogen is continued through reactor 202 forapproximately l minutes, at which time the reactor is blocked of anddepressured to the low pressure separator (not shown). Steam is thenintroduced for 5 minutes. At the end of this period the valvescontrolling the conveyor system are opened and the catalyst is passed tothe regenerator at such a rate that about 45 minutes or less arerequired to empty the reactor. The system is then reversed and for about45 minutes or less the reactor is supplied with the required amount ofcatalyst of the desired temperature. Catalyst iiow is stopped and steamcontinued to vent line M6 for 5 minutes, at which time vent valve 2M isclosed off `and hydrogen or propane is cut into repressure reactor 202.Hydrogen flow is established and oil cut in approximately 2 hours fromthe time oil iiovv was stopped. At this point, reactor |58 has beenon-streain 4 hours and now undergoes the cycle steps described forreactor 2&2. Where the process is operated continuously, as in thedescription given above, all valves involved in the switching operationsare desirably time cycle controlled, i. e., these valves are set to beoperated automatically after a certain period of time has elapsed.

As stated above, a greater or lesser number of reactors may be employedas desired. It will be obvious that a system employing a ll-hourprocessing period and a 2-hour non-processing period, i. e., hydrogenpurge, steaming, depressuring, transfer of deactivated catalyst out andregenerated catalyst in, and repressuring, may be carried outcontinuously with only two reactors. However, by increasing the numberof reactors by one-half, or to a total of three, the yield may bedoubled without increasing the size of the conveyor system, since tworeactors will be on-stream at all times. On the other hand, if thenumber of reactors is increased to four with the same time of processingand regeneration, two reactors would be on-stream part of the time andthree reactors on-stream during another part of the time. In such amodification, however, two reactors would be cifstream simultaneously,in which case the size of the conveyor system would necessarily have tobe doubled. Accordingly, the most desirable operation would employ abalance between the amount of yield, the number and size of reactors,and the size of the conveyor system. I-lowever, a system employing fouror more reactors and one regenerator may be utilized successfully,Without increasing the size of the conveying system, by reducing thetime required for catalyst transfer. It should be noted that thestructure of the conveyor system employed in my apparatus is notdictated by problems of the amount of heat to be transferred to thereactor as in conventional iuidized catalytic cracking systems, butmerely by considerations of transferring the required amount of catalystin the optimum economic time.

As stated above, my process is applicable to any 4catalytically promotedchemical reaction which utilizes elevated pressure, which has a heat ofreaction varying from approximately neutral to exothermic, and in whichthe catalyst is reactivated by oxidation. In carrying out ahydroforniing reaction, for example, where hydrogen is present but notconsumed substantially, line II, pump I2, and line IG may or may not beemployed to introduce hydrogen. When carrying out other processes notinvolving hydrogenation, line I I, pump I2 and line Ill may be utilizedto introduce a reactant other than hydrogen and other than thatintroduced into the system through line I. It is also sometimesdesirable to employ a iiow of diluent iiuid in exothermic reactions forthe purpose of temperature control within the reactor, even in instanceswhere the fluid is not consumed. In such instances, the apparatus asillustrated could be employed with the uid entering the system throughline II, pump I2 and line III, while the reactant or reactants enterthrough line I, pump 2 and line c.

In general, I contemplate using catalysts and working conditions usuallyemployed with the specific type of process being carried out in myapparatus. These catalysts and conditions are well known to the art, andtherefore, it is not considered necessary to list them in detail.I-Iowever, or purposes of illustration, a few examples of catalystswhich may be used in preferred modifications will be given. In onepreferred form of my invention wherein a hydrocracking process iscarried out, examples of satisfactory catalysts are oxides of vanadium,chromium, tungsten, aluminum, titanium, magnesium, molybdenum andzirconium, advantageously composited with a carrier to give the desireddensity and size for iiuidized-nxed bed operations. '.lhese catalystsare merely given by way of example. Other catalysts may ce used withequal facility. 1n general it appears that any catalyst having bothnydrogenating and cracking properties may be employed.

I consider my process to be or' particular value in connection with onespecies of hydrogenation, namely catalytic hydrodesulfurizaticn.Examples of satisfactory catalysts which may be employed in my processas applied to catalytic hydrodesulfurization are: heavy metalaluminusilicates, cobalt thiomolybdate, tungsten-nickelsulfide,tungsten-iron-sulde, nickel, nickel oxide, nickel sulde, molybdenumoxide-zinc oxidemagnesia, molybdenum oxide-chromium oxide,nickel-copper-alumina, molybdic oxide-nickeliferous oxide, molybdicoxide, copper oxide, cobalt molybdate, molybdic sulfide and tungstensulde, each being advantageously composited with a carrier. Nickel,iron, cobalt, their oxidesI chromates, molybdates and tungstates arevery satisfactory hydrodesulfurization catalysts.

The porous support or carrier mentioned above (which may possess somecatalytic activity) may be any conventional material for this purpose,such as microspheres of a synthetically prepared silica-alumina crackingcatalyst or powdered activated alumina or silica-alumina. Powderedsilica gel, kieselguhr, and acid treated pumice are further examples ofsatisfactory supports for the above listed catalysts. Other powderedsynthetically prepared carriers which may be used are silica-Zirconia,silica-titania, alumina-titania, and silica-alumina-boric oxide. Thesecarriers may be prepared by coprecipitation or impregnation.

The composited catalysts may be made by impregnating the microspheroidalor powdered carrier with a solution of a soluble salt of the metal, suchas a nitrate, followed by calcining to form the oxide and followed byreduction if a metal or mixture of metal and metal oxide is to be used,or by sulilcling where a suliide catalyst is desired. Also porousparticles impregnated with one metal or metal oxide may be employed inadmixture with porous particles impregnated with one or more othermetals or oxides. in order that the catalyst may be maintained in aturbulent, suspended condition, the size of the individual particlesshould not substantially exceed about 60 mesh, i. e., about 0.833millimeter in diameter,

The on-stream period for the individual reactor should be terminatedwhen the activity of the catalyst has been substantially reduced. Inconnection with most of the catalysts listed above, the reduction ofcatalyst activity is due primarily to coke laydown, i. e., acarbonaceous deposit on the catalyst resulting from cracking. Obviously,burning off this layer of carbon, as carried out in the regenerator,operates to reactivate the catalyst in such instances. in the instanceof certain metal or oxide catalysts for hydrodesulfurization processes,sulding of the metal or oxide contact may occur. The regenerationtreatment in this type of process burns off the carbonaceous deposit aswell as the sulfur.

The temperature range for operations in accordance with my inventionvaries depending upon the reaction involved, i. e., the temperature isthat which is conventional for the particular reaction. For example, atemperature range between about l F. and about 600 F. is generally usedfor non-destructive hydrogenation. Destructive hydrogenation usuallyinvolves a temperature between about 600 F. and about l000 F. Atemperature range of about 225 F. to about 650 F. is usually employed inconnection with polymerization reactions, the temperature varyingaccording to the particular catalysts and pressures employed. As regardsthe destructive hydrogenation of heavy charge stocks, such as total orreduced crude, a preferred embodiment of my invention, temperaturebetween about '750 F. and 950 F. are most useful and especially thosebetween about 800 F. and 870 F. However, lower or higher temperaturescan be used.

The pressure employed may vary quite widely from about 100 p. s. i. g.to about 3000 p. s. i. g., again depending on the reaction involved.Pre..- sures in the lower portion of this range are preferred foreconomic reasons, and since the catalyst bed may be maintained influidized condition more easily at lower pressures. At the same timethese pressures are suicient to pro- 12 duce a satisfactory rate ofhydrogenation in modifications of my pro :ess which employ hydrogen,such as hydrocracking or hydrodesuliurization.

rl'he hydrogen to oil ratio may be varied over an extremay wide range inprocesses involving hydrogen treatment of hydrocarbons, but ispreferably between about 300 and about 20,000 s. c. f./bbl. (standardcubic feet per barrel). Higher ratios are preferred in connection withtreatment of heavier charge stocks. I have found that any hydrogenpurity above about 50 per cent produces satisfactory results inmodifications of my process which involve hydrocracliing. The throughputmay vary from 1-12. In all instances, however, the rates of now of thereactants, e. g., hydrogen and charge stock, are correlated to produce aiixed nuidized catalyst bed.

Any reactant which exists in gaseous, vapor, or partly Vapor form atreaction conditions may be employed as a reactant vapor, so long as itor they produce an approximately neutral to exothermic reaction, and solong as the catalyst may be regenerated by oxidative action. rlhus, byreactant vapor in the accompanying description and the appended claims lmean a substance or substances answering to this description.

As regards hydrocarbons, my invention is applicable to any charge stock,so long as it may exist at lea-st partly in vapor form at reactionconditions. However, my invention is particularly useful as applied tothe conversion oi heavy charge stocks such as total, reduced or toppedcrude, and especially those of low API gravity and high sulfur content,since these stocks require high treating temperatures, the use of whichproduces increased coke laydown. Since my invention is particularlyapplicable to processing conditions involving regeneration to removerelatively large amounts of contaminants, these heavy stocks can beeconomically processed.

Regeneration of the catalyst is carried out at a temperature sufiicientto remove contaminants or otherwise restore the activity of the catalystbut insuiiicient to cause physical damage to the catalyst particles.When reactivation is carried out so as to burn off a carbonaceousdeposit, this temperature preferably varies from about 1000 F. to about1200o F.

While regeneration under pressure is desirable from a rate standpoint,economical considerations and the mechanical difficulties involvedindicate the preferred regeneration pressure to be below about 50 p. s.i. g., i. e., substantially atmospheric pressure.

The rate of flow of the reactants through the catalyst bed in either thereactor or the regenerator may vary widely. In general, the upper limitis governed only by the time of contact desired, the contact time beingmore or less inversely proportional to the rate of flow of thereactants. The rate of iiow may be so great, for example, as to impartviolent turbulence, ebullition and/or random motion to the particlesthroughout the reactor. This type of motion may be termed trueluidization. In these instances a larger portion of the catalyst may beblown out of the reactor and returned through the cyclones. The rate offlow should be at least great enough to suspend the particles andproduce a moderate turbulence or ebullition. A rate of dow in or nearthis portion of the range produces what may be termed expanded bedoperation. Any of the above described degrees of turbulence may be usedin the reactor or regenerator, with the same or a different degree ofturbulence being employed in the respective vessels. Specific iiow ratessuncient to produce the turbulence described vary according to the sizeof the catalyst particles, their density, and the width and depth of thecatalyst bed. In certain reactions, e. g., hydrocraclring of heavyhydrocarbons, where the charge stock is converted with greaterdiiliculty, a low rate or now of the reactants into the reactor ispreferable `Where more complete conversion is desired, since this allowsat least a portion of the more diirlcultly convertible hydrocarbons toremain under reaction conditions for a longer period of time. Wherecatalyst deactivation is due to a large degree of coke laydown, andwhere the regeneration comprises burning off this coke, as inhydrocracking of heavy charge, for example, true uidization of thecatalyst particles in the regenerating vessel is advantageous. This isbecause a more rapid rate of flow through the catalyst bed isadvantageous to rapidly regenerate and eiectively remove a part of theheat of combustion, thus preventing damage to the catalyst due tooverheating.

In these facts lie one of the principal advantages of my process over afluidized xed bed process in which the catalyst is regenerated Withinthe reactor. Since it is advantageous to regenerate the catalyst undertrue fluidized conditions, the catalyst, during regeneration, occupiesmuch more space than it occupies during the on-stream period, Where mereexpanded bed conditions may exist. If the catalyst Were regenerated inthe reactor, the reactor would necessarily have to be much larger toaccommodate the additional volume required by the catalyst during thetrue fluidization present during regeneration. By providing a separateregeneration vessel, I may reduce the size of the expensive pressurereaction Regenera- Regeneration in same tion in sepavessel rate vesselNumber of reactors 13 10 Reactor height 75 @5 Total reactor height 9753.30

Thus, in the proposed apparatus a saving of 625 feet of expensiveheavy-Walled pressure vessel is made possible.

I do not intend to be limited to the particular details of structure asillustrated in the drawing. For example, the charge stock and hydrogenor other reactant may be preheated separately and introduced separatelyinto the reactor.

In a preferred form of my invention one or more additional charges icatalyst are maintained in the regenerator. When the on-stream cycle ofa given reactor has been terminated and the deactivated catalyst hasbeen completely removed to the regenerator, the reactor which has beenemptied is quickly refilled with the mixture of regenerated catalystsoriginally in the regen-f erator and the partially regenerated catalystobtained from the reactor. Thus the reactor is refilled with catalyst ofhigh average activity before regeneration of all the deactivatedcatalyst is fully complete. As a result of this the reactor may beplaced on-stream again quickly even in instances Where coke laydown isvery great. This reactor is then repressurcd and placed oil-streamagain, while the remaining deactivated catalyst withdrawn from thereactor is being regenerated. In this manner the reactors are oir-streamfor a shorter period of time, and more ecient use is made oi theseexpensive vessels. In this modication, the regenerator may operatecontinuously, thus eliminating the necessity for repeatedly starting upcombustion. The maintenance of an extra amount of catalyst in theregenerator also prevents great iluctuation in the level of the catalystbed therein.

Whether or not extra catalyst is maintained in the regenerator, Icontemplate either completely regenerating all or the deactivatedcatalyst prior to the return of any catalyst to the reactor, or promptreturn of catalyst to the reactor with regeneration being carried out inthe regenerator during catalyst transport.

One advantage of my invention is that it provides an improvedregenerating method for luidized-red bed processes, wherein carbonaceousdeposition on the catalyst is very great. I have also provided a processin which regeneration of the catalyst is less of a problem, since thepossibility of plugging of the catalyst bed through coke laydovvn hasbeen eliminated. My invention also produces an improved catalystregeneration method whereby the catalyst may be regenerated atsubstantially atmospheric pressure, although the reaction is carried outat elevated pressure. Another advantage produced by my invention is thatthe need for inert cooling gas during regeneration is eliminated, sincethe danger of catalyst damage resulting from overheating duringregeneration has lbeen lessened. Still another advantage is that l haveprovided an apparatus in'which the structure of the conveyor syst-embetween reactor and regenerator is not dictated by the amount of heat tobe transferred to the reactor. A further and important advantage of myprocess and apparatus is that the cost oi the equipment is reducedsubstantially by reducing the insulation requirements for the reactors.I have also provided a continuous method and apparatus therefor,embodying the advantages listed above. I have further provided a methodand apparatus wherein a substantial saving is eiected by regenerating ina vessel l separate from the reaction vessel.

What I claim is:

l. In a process for catalytically promoting a chemical reaction, whereinthe heat of reaction ranges from approximately neutral to eXothermic andin which the catalyst is reactivated by oxidation, the step-s comprisingmaintaining powdered refractory catalyst in a state of turbulentsuspension within a reaction chamber, contacting said catalyst with astream of reactant vapor under conditions of elevated temperature andpressure, continuously withdrawing converted product while retainingsubstantially all of the catalyst within the reaction chamber,terminating the reaction cycle when the activity of the catalyst hasbeen substtantially reduced, depressuring the reaction chamber, removingthe catalyst to a regenerating zone, regenerating the catalyst byaceaeee subjectinit to an oxidizing treatment at ele,

vated temperature and at a substantially lower pressure while in stateof turbulent suspension, contir -i..ously cooling the catalyst in theregenerator, removing regenerated catalyst from the regenerating zone,cooling the removed regenerated catalyst to reaction temperature in acooling zone, returning regenerated and cooled catalyst to the reactionchamber, repressuring the reaction charnber, again utilizing the cooledand regenerated catalyst to promote said approximately neutral toexothermic reaction, and continuously circulating hot regeneratedcatalyst through said cooling zone during such periods as the catalystis not being returned to the reactor to avoid thermal strains that wouldbe encountered by intermittent passage of hot catalyst there'lhrough.

2. in a process for catalytically promoting a chemical reaction, whereinthe heat of reaction ranges from approximately neutral to exothermic andin which the catalyst is reactivated by oxidation, the steps comprisingpassing a reactant vapor upwardly through a bed of powdered reractc rycatalyst within a reaction chamber at a rate suiicient to produce onlymoderate turbulence of the catalyst particles and in order to intimatelyContact the catalyst with said charge stock, said contacting beingcarried out under conditions of elevated temperature and pressure,continuously withdrawing converted product while retaining substantiallyall of the catalyst within the reaction chamber, terminating thereaction cycle when the activit37 of the catalyst has been substantiallyreduced, depressuring the reaction chamber, removing the catalyst to aregenerating chamber, regenerating the catalyst by passing an oxidizinggas upwardly through the regenerating chamber at a rate suilicient toproduce considerably greater turbulence of the catalyst particles thanis produced in the reaction chamber, said regeneration taking place atelevated temperature and at a substantially lower pressure, removingregenerated catalyst from the regenerating chamber, returningregenerated catalyst to the reaction chamber, repressuring the reactionchamber, and again utilizing the regenerated catalyst to promote saidapproximately neutral to exothermic reaction.

3. In a process for catalytically promoting a chemical reaction, whereinthe heat of reaction ranges from approximately neutral to exothermic andin which the catalyst is reactivated by oxidation, the steps comprisingmaintaining powdered refractory catalyst in a state of turbulentsuspension within a reaction chamber, contacting said catalyst with astream of reactant vapor under conditions of elevated temperature andpressure, continuously withdrawing converted product while retainingrsubstantially all of the catalyst within the reaction chamber,terminating the reactlon cycle when the activity of the catalyst hasbeen substantially reduced, depressuring the reaction chamber,Y removingthe catalyst to a regenerating zone which contains an extra charge ofpowdered catalyst which is continuously undergoing oxidativeregeneration while in a state of turbulent suspension at a substantiallylower pressure than exists in the reactor, removing a mixture ofregenerated and unregenera-ted catalyst from the regenerating zone,introducing this removed mixture into the reactor promptly aftertermination of removal of inactive catalyst from the reactor and Whilepart of the inactive catalyst removed from the reactor is stillundergoing regeneration, promptly repressuring ie reaction chamber andagain utilizing the regenerated catalyst to promote said approximatelyneutral to exothermic reaction.

PAUL W. CORNELL.

References Cited in the 111e of this patent UNITED STATES PATENTS NumberY Name Date 2,265,837 Harding Dec. 9, 1941 2,273,864 Houdry Feb. 24,1942 2,356,717 Williams Aug. 22, 1944 2,417,154 Huber Mar. 11, 19472,434,537 Barr et al. Jan. 13, 1948 2,515,373 Keith et al July 18, 19502,546,625 Bcrtstrom Mar. 27, 1951 2,585,238 Gerhold Feb. 12, 1952FORETGN PATENTS Number Country Date 383,616 Great Britain Feb. 13, 1931

3. IN A PROCESS FOR CATALYTICALLY PROMOTING A CHEMICAL REACTION, WHEREINTHE HEAT OF REACTION RANGES FROM APPROXIMATELY NEUTRAL TO EXOTHERMIC ANDIN WHICH THE CATALYST IS REACTIVATED BY OXIDATION, THE STEPS COMPRISINGMAINTAINING POWDERED REFRACTORY CATALYST IN A STATE OF TURBULENTSUSPENSION WITHIN A REACTION CHAMBER, CONTACTING SAID CATALYST WITH ASTREAM OF REACTANT VAPOR UNDER CONDITIONS OF ELEVATED TEMPERATURE ANDPRESSURE, CONTINUOUSLY WITHDRAWING CONVERTED PRODUCT WHILE RETAININGSUBSTANTIALLY ALL OF THE CATALYST WITHIN THE REACTION CHAMBER,TERMINATING THE REACTION CYCLE WHEN THE ACTIVITY OF THE CATALYST HASBEEN SUBSTANTIALLY REDUCED, DEPRESSURING THE REACTION CHAMBER, REMOVINGTHE CATALYST TO A REGENERATING ZONE WHICH CONTAINS AN EXTRA CHARGE OFPOWDERED CATALYST WHICH IS CONTINUOUSLY UNDERGOING OXIDATIVEREGENERATION WHILE IN A STATE OF TURBULENT SUSPENSION AT A SUBSTANTIALLYLOWER PRESSURE THAN EXISTS IN THE REACTOR, REMOVING A MIXTURE OFREGENERATED AND UNREGENERATED CATALYST FROM THE REGENERATING ZONE,INTRODUCING THIS REMOVED MIXTURE INTO THE REACTOR PROMPTLY AFTERTERMINATION OF REMOVAL OF INACTIVE CATALYST FROM THE REACTOR AND WHILEPART OF THE INACTIVE CATALYST REMOVED FROM THE REACTOR IS STILLLUNDERGOING REGENERATION, PROMPTLY REPRESSURING THE REACTION CHAMBER ANDAGAIN UTILIZING THE REGENERATED CATALYST TO PROMOTE SAID APPROXIMATELYNEUTRAL TO EXOTHERMIC REACTION.